Default [Q] Problem with dust

Well as the title asks i need some help-tips on how to clean my s2 from the inside.
When i opened the backcase the dust would be seen with blind eyes but i think it cant be cleared by removing only the battery.I need to open the whole back part and clean it somehow.
That might be the reason i am getting massive lags while using it.(the dust)
Okay,anyway if someone knows how to do this let me know greets!

P.S: I am sorry if this has already been asked in the past or i am asking in a wrong place but i am new there and i am trying to get used to!